Thursday, June 11, 2009

DWEB? (Driving While Eating Bread)

I got saw this link from a Pennsylvania DUI lawyer.

So, apparently bread makes you test positive for alcohol on the breath. That's a quandary, indeed. I wonder the science behind this. Moreover, I wonder how the DUI lawyer found this out.
Posted by Leo M Mulvihill, Jr at Thursday, June 11, 2009

1 comments:

Justin J. McShane said...

Thank you for tracking my post and my video. I was actually exposed to it at a national training seminar many years ago presented by the National College for DUI Defense.

The origin, as in the first person that I know of who figured out the false positive due to eating normal bread, was an attorney in Alabama by the name of Phil Price. I can create the false positive all day long. On this day all of the results were over a .02 and the one on the video was not actually the highest.

The science behind it is relatively inelegant. This false positive occurs because of the simple fact that these devices and even the full evidential breath test devices do not truly measure alcohol (ETOH). They measure using the science of infrared breath test spectrometry or fuel cell technology. An infrared based device is a photo electric device, capable of collecting a sample of deep lung air, analyzing it, and expressing the concentration in a certain measure. In essence the machine measures certain parts of the molecule (at certain wavelengths) in the infrared spectrum. The problem is that the manufacturer has selected to look for wavelengths that several other substances also have in common. Therefore, it is not specific to alcohol.

Fuel cell censors are true electrochemical devices. They oxidize (remove one or more electrons from the compound in question) the substance to be analyzed, in this case they want to capture ethanol, on a catalytic surface- a platinum electro. A platinum electro forms a anode (a positive electrode of the device the point of departure for the electrical energy from the fuel cell) of the fuel cell. The other side of the cell reduces atmospheric oxygen at the platinum cathode (the negative electrode of the device, the point of entry of electrons into the fuel cell) – the counter-electrode in these cells. The two platinum electrodes are separated and supported by a thin porous disc that is impregnated with electrolyte solution of acidic acid. The fuel cell is designed to produce a self-sustaining electro-oxidation of ethanol adecel cathode initiating electron flow and therefore current generation to the anode. The problem then again is that it too is not specific to alcohol.

It is a big problem for people. Thanks again for picking up the post.

June 12, 2009 8:26 AM

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